This invention relates generally to a lawn mower and, more particularly, to an air-circulation lawn mower wherein grass clippings are carried with carrier air into a grass bag via a carrying passage and only air is returned into a cutter deck of a mower body via an air return passage extending from the grass bag to the cutter deck.
Air-circulation lawn mowers are disclosed in, e.g., Japanese Utility Model Laid-Open Publication No. SHO-63-66423 entitled xe2x80x9cAnti-dust-scattering Structure for Grass Cutting Machinexe2x80x9d and Japanese Utility Model Laid-Open Publication No. SHO-63-71622 entitled xe2x80x9cGrass Collecting Device for Grass Cutting Machine.xe2x80x9d
The grass cutting machine of SHO-63-66423 is configured to produce an airflow by sucking air inside from the outside of a cutting blade casing, discharge grass cut by the cutting blade into a catcher with the airflow and circulate air from the catcher into the cutting blade casing.
This grass cutting machine is, however, configured to return air into the center of the cutting blade casing. Since a drive member for rotating the cutting blade is positioned in the midsection of the cutting blade casing, it is necessary to form a circuitous path around the drive member or prevent leakage of air, resulting in a complicated structure.
The grass cutting machine of SHO-63-71622 is configured to form an air circulation path by connecting a discharge opening of a cutting section and an intake of a grass bag with a grass carrying passage and connecting the grass bag and the cutting section with an air passage B.
However, the grass collecting device of this grass cutting machine is configured to return air into a rear portion of the cutting section 5, and requires right angle bending of airflow returned into the cutting section, undesirably causing pressure loss. Further, the grass collecting machine is configured to discharge air outside, producing large noise and discharging dust.
In this context, a lawn mower which allows sufficient production of pressure differential for returning air into a cutter deck and allows reduction in pressure loss is desired.
According to the present invention, there is provided a lawn mower, which comprises a mower body; a drive source mounted on the mower body; a cutter blade driven by the drive source for rotation, the cutter blade having airlifts at opposite ends thereof; and a grass bag provided at the rear of the mower body for receiving grass cut by the cutter blade. The mower body comprises a cutter deck accommodating the cutter blade in a rotatable manner; a grass carrying passage for guiding grass cut by the cutter blade into the grass bag; and an air return passage for guiding only air from the grass bag into the cutter deck, the air return passage being formed on an upper surface of the cutter deck, and a cutter deck-facing opening of the air return passage being arranged in line with the rotating track of the airlifts.
In order to return air inside the grass bag into the cutter deck, effective pressure differential is required between the grass bag and the cutter deck. In the present invention, the air return passage is formed on an upper inside surface of the cutter deck and the cutter deck-facing opening of the air return passage is opposed to the rotating track of the airlifts of the cutter blade. Return air is thus drawn from the cutter deck-facing opening into the cutter deck by use of a swirling flow caused by the rotation of the cutter blade. This allows efficient air circulation from the grass bag toward the inside of the cutter deck, resulting in reduction in noise of the lawn mower and dust.
The cutter deck-facing opening of this invention is preferably oriented such that air jetting out from the opening is in line with a flow of air inside the cutter deck produced by rotation of the cutter blade. This eliminates a counter flow against a flow of air produced inside the cutter deck, leading to a smooth flow of air inside the cutter deck. In particular, disposing the cutter deck-facing opening on the opposite side of the grass carrying passage with a rotating shaft of the cutter blade interposed therebetween reduces pressure loss at the air return passage.
A grass bag-facing opening of the air return passage is opened upward. This facilitates separation between grass clippings and carrier air.
The grass bag of this invention preferably comprises a permeable partition wall separating the grass carrying passage and the air return passage, thereby having separated upper and lower chambers, the upper chamber being connected to the air return passage and the lower chamber being connected to the grass carrying passage. That is, separating the grass bag into upper and lower chambers by forming the permeable partition wall prevents grass clippings from entering the upper chamber so that only air with glass clippings removed is returned into the cutter deck.
The cutter deck-facing opening of this invention may be formed not to protrude toward the cutter deck, or may have a front end cut and bent upward and a rear end cut and bent downward, or may comprise two openings formed by cutting and bending downward a portion ahead of the midpoint of the opening and cutting and bending upward a portion behind the midpoint.